Astronauts working early Sunday morning outside the International Space Station (ISS) ran into problems with bolts and washers popping free, causing Mission Control to revise the spacewalkers' plan for greasing a joint that rotates the orbiting laboratory's power-providing solar arrays.
Shuttle Endeavour astronauts Andrew Feustel and Mike Fincke ventured outside the station tasked with topping off the complex's slowly-leaking coolant system and lubricating the left-side solar arrays' rotary joint.
Work on the earlier proceeded smoothly but it wasn't long before the bolts began flying on the latter.
"Mike, the status of bolt 1, [do] you have it?" asked Greg Chamitoff, the spacewalk's choreographer, to Fincke, who was working to free thermal covers covering the joint's mechanism.
"No, it went to heaven," replied Fincke.
Feustel, working nearby on the coolant system refill, spotted the bolt as it slowly floated toward the left side of the station. Astronauts working inside the space station were able to photograph the bolt and send the images to Mission Control.
At least four other bolts came free from the thermal covers, but Fincke was able to catch them before they floated away.
As viewed from his helmet cam, Fincke holds a rotary joint cover and its bolt.
"[Fincke] was doing a great job at being gentle. Again he gets the golden glove award for another catch. That was fantastic," said Mission Control. "We really don't have a good answer for why that is happening."
The retaining washers that were designed to hold the bolts in place were either missing or bent, reported Fincke. One of the washers that was still present came free and was also lost.
As a result, Mission Control decided to have the spacewalkers open only four of the six covers that were originally planned and take extra caution while doing so.
"We're going to minimize the number of covers we're going to take off," said spacecraft communicator Steven Swanson from on Mission Control in Houston. "We'd like though, as [Fincke] takes them off, to go to seven turns [with a power tool] and then if possible, use his hands to gently turn the next two turns until [the bolt] pops up."
"I'd like to be even more methodical than usual on these. We'll get the job done and be even more careful," said Fincke.
That method seemed to work, as no other bolts or washers were lost and the astronauts were able to move ahead with using grease guns to apply lubrication to the rotary joint.
In 2007, the joint's right-side counterpart was found to be grinding against itself, depositing metal fragments in the mechanism, slowing its rotation. A 2008 space shuttle Endeavour mission had spacewalkers apply grease to the joints, resolving the problem.
The waterwheel-like joints now need to be periodically greased, which is what Fincke and Feustel was working to do today.
With the coolant system refilled and the rotary joint partially lubed, the spacewalkers were scheduled to install two stowage beams for a radiator and add a camera cover and lubricate the hand of the Canadian-built two armed robot, Dextre.
Meanwhile, as they do that work, Mission Control will remotely command the station's left-side Solar Alpha Rotary Joint to rotate so the grease applied by the astronauts will be spread evenly around the ring. If time allows at the end of the spacewalk, Fincke and Feustel will return to the rotary joint to apply even more lubrication and then reinstall the covers they removed earlier.